Determinants and Mechanisms of the Renin-Aldosterone Stress Response

Increased daytime and awakening salivary free aldosterone in essential hypertensive men

Background

While aldosterone plays an important role in blood pressure regulation, its role in essential hypertension (EHT) remains unclear. Here, we systematically investigated the secretion of biologically-active free aldosterone in saliva in response to awakening (AldAR) and during the day (AldDay) in EHT compared to normotensive controls (NT).

Methods

In 30 men with EHT and 30 age-matched NT, AldAR saliva samples were collected immediately after awakening and 15, 30, 45, and 60 min thereafter and AldDay samples were collected from 08:30-22:00 h on two consecutive days.

Results

Over the course of the day, men with EHT had higher repeated AldDay levels compared to NT (p = .002) with higher concentrations in the morning hours (p's ≤ .047), a steeper decline over the course of the day (p's ≤ .018), and similar concentrations in the evening (p's ≥ .21). Regarding AldAR, we observed higher concentrations in EHT at awakening (p = .017) and borderline higher concentrations at 15 min (p = .086). No differences were found 30-60 min after awakening (p's ≥ .34). Analyses with repeated and aggregated AldAR levels resulted in borderline significantly higher free aldosterone in EHT (p's ≤ .077). Complementary analyses confirmed linear associations between higher blood pressure and higher AldAR and AldDay levels.

Conclusions

Our data point to elevated salivary free aldosterone secretion in EHT over the course of the day, particularly in the morning hours. As the free aldosterone fraction is considered biologically active, our data may point to a biological mechanism underlying EHT.

Is your stress my stress? A standardized, randomized-controlled paradigm to study physiological stress contagion based on direct stress observation

BACKGROUND & OBJECTIVES

Existing research indicates that not only own stress leads to physiological stress reactions, but also observing stress in others. So far, a standardized paradigm to reliably induce physiological stress contagion based on direct face-to-face stress observation compared to an active placebo-stress observing control condition is lacking. Here, we tested a standardized randomized placebo-controlled experimental paradigm to investigate physiological reactivity to direct stress observation and characterized the stress contagion response of the major endocrine stress systems, including full reactivity kinetics.

METHODS

Healthy young male participants were randomly assigned to (1) undergo an adapted version of the Trier Social Stress Test ("TSST participants", n = 20), (2) observe it ("stress observers", n = 36), or (3) observe a corresponding placebo-stress control condition ("placebo-stress observers", n = 30). We repeatedly assessed heart rate, salivary alpha-amylase, salivary cortisol, and salivary aldosterone.

RESULTS

Stress observers exhibited greater physiological reactivity to stress observation as compared to placebo-stress observers to placebo-stress observation in heart rate, salivary alpha-amylase, and cortisol (p's ≤ .027), but not in aldosterone. We observed similar reactivity kinetics in TSST participants and stress observers but less pronounced in stress observers.

DISCUSSION

Extending previous literature, our findings indicate that independent of secondary effects of the observation setting, direct observation of stress in other individuals induces activation of the hypothalamus-pituitary-adrenal axis and the sympathetic-adrenal-medullary axis. Moreover, the physiological stress contagion response resembles the physiological reactivity to first-hand stress but is less pronounced. Potential implications of physiological stress contagion regarding health, cognition, or behavior, as well as modulating factors need to be further elucidated.

Unstable Housing and Mortality Among US Veterans Receiving Dialysis

Importance

Housing status is an important health determinant, yet little is known about unstable housing among individuals receiving dialysis.

Objective

To determine factors associated with unstable housing among US veterans receiving dialysis and to estimate the association of unstable housing with risk of death.

Design, Setting, and Participants

This retrospective cohort study used data from the US Veterans Health Administration (VHA) and the US Renal Data System for patients who initiated dialysis between October 1, 2012, and December 31, 2018. Veterans were included if they used VHA outpatient services and completed 1 or more unstable housing screenings within a 3-year period before starting dialysis. Data analysis was conducted from January 24 to June 16, 2023.

Exposures

Unstable housing was defined as self-report of not having stable housing within the past 2 months or having concerns about stable housing in the next 2 months.

Main Outcomes and Measures

The main outcome was all-cause mortality. Characteristics associated with unstable housing at the time of dialysis initiation were examined. The multivariate Fine and Gray cumulative incidence model was used, treating transplant as a competing risk and age as an effect modifier, to examine the risk of death associated with unstable housing.

Results

This study included 25 689 veterans, with a median age of 68 (IQR, 62-74) years. Most participants were men (98%), and more than half (52%) were White. There were 771 veterans (3%) with a positive screen for unstable housing within a 3-year period before starting dialysis. Compared with veterans with stable housing, those with unstable housing were younger (mean [SD] age, 61 [8] vs 68 [10] years), were more likely to be Black (45% vs 32%) or Hispanic (9% vs 7%), and were more likely to start dialysis with a central venous catheter (77% vs 66%), receive in-center hemodialysis (96% vs 91%), and have non-Medicare insurance (53% vs 28%). Factors associated with unstable housing included Hispanic ethnicity, non-arteriovenous fistula vascular access, lack of predialysis nephrology care, and non-Medicare insurance. Veterans with unstable housing had higher all-cause mortality (adjusted hazard ratio [AHR], 1.20 [95% CI, 1.04 to 1.37] for a median age of 68 years), and risks increased with age (P = .01 for interaction). In age-stratified analyses, unstable housing was associated with higher mortality among veterans aged 75 to 85 years (AHR, 1.64 [95% CI, 1.18 to 2.28]), but associations were not observed for other age groups.

Conclusions and Relevance

In this cohort study of veterans receiving dialysis, unstable housing experienced before starting dialysis was associated with increased risk of all-cause mortality, and risks increased with age. Further efforts are needed to understand the experiences of older adults with unstable housing and to estimate the scope of unstable housing among all individuals receiving dialysis.

A randomized vagus nerve stimulation study demonstrates that serum aldosterone levels decrease with age in women, but not in men

In this randomized, sham-controlled study, we explored the effects of acute transcutaneous vagus nerve stimulation (tVNS) on serum aldosterone in 20 younger (21-26 years) and 19 older (40-70 years) healthy participants. Blood samples were collected on two different days before and after a 20-min application of active tVNS at the inner tragus or sham stimulation of the earlobe. Irrespective of the stimulation mode, aldosterone levels decreased from pre- to post-stimulation in both the young (active: β = - 1.610 (- 2.855, - 0.365), p = 0.022; sham: β = - 0.857 (- 2.102, 0.388), p = 0.257) and the old cohort (active: β = - 1.969 (- 3.234, - 0.703), p = 0.005; sham: β = - 1.334 (- 2.600, - 0.069), p = 0.063). Although this decline was significant during active tVNS, the difference in estimated β-coefficients between active and sham stimulation was not statistically significant in either cohort. Nevertheless, aldosterone concentrations showed a significant interaction effect between sex and age (p = 0.001). Among all study participants, younger women (23.3 ± 1.6 years) had the highest mineralocorticoid levels (pre active: 172.1 ± 102.0 pg/ml, pre sham: 214.3 ± 82.3 pg/ml), whereas the lowest were observed in older females (59.4 ± 9.4 years) (pre active: 104.9 ± 85.8 pg/ml, pre sham: 81.1 ± 53.8 pg/ml). This post hoc analysis did not suggest that active auricular tVNS reduces serum aldosterone levels compared to sham stimulation in healthy subjects. However, serum aldosterone levels differed among subjects depending on their age and sex, irrespective of tVNS.

Physiological reactivity to acute mental stress in essential hypertension-a systematic review

Objective

Exaggerated physiological reactions to acute mental stress (AMS) are associated with hypertension (development) and have been proposed to play an important role in mediating the cardiovascular disease risk with hypertension. A variety of studies compared physiological reactivity to AMS between essential hypertensive (HT) and normotensive (NT) individuals. However, a systematic review of studies across stress-reactive physiological systems including intermediate biological risk factors for cardiovascular diseases is lacking.

Methods

We conducted a systematic literature search (PubMed) for original articles and short reports, published in English language in peer-reviewed journals in November and December 2022. We targeted studies comparing the reactivity between essential HT and NT to AMS in terms of cognitive tasks, public speaking tasks, or the combination of both, in at least one of the predefined stress-reactive physiological systems.

Results

We included a total of 58 publications. The majority of studies investigated physiological reactivity to mental stressors of mild or moderate intensity. Whereas HT seem to exhibit increased reactivity in response to mild or moderate AMS only under certain conditions (i.e., in response to mild mental stressors with specific characteristics, in an early hyperkinetic stage of HT, or with respect to certain stress systems), increased physiological reactivity in HT as compared to NT to AMS of strong intensity was observed across all investigated stress-reactive physiological systems.

Conclusion

Overall, this systematic review supports the proposed and expected generalized physiological hyperreactivity to AMS with essential hypertension, in particular to strong mental stress. Moreover, we discuss potential underlying mechanisms and highlight open questions for future research of importance for the comprehensive understanding of the observed hyperreactivity to AMS in essential hypertension.

AT1R blocker prevents mental stress induced retrograde blood flow in overweight/obese men

The main goal was to determine the impact of mental stress (MS) on blood flow regulation in overweight/obese men. Fourteen overweight/obese men (27 ± 7 years; 29.8 ± 2.6 kg/m² ) participated in two randomized experimental sessions with oral administration of the AT1R blocker Olmesartan (40 mg; AT1RB) or placebo (PL). After 2 h, a 5-min acute MS session (Stroop Color Word Test) was administered. Blood flow was assessed at baseline and during the first 3 min of MS by vascular ultrasound in the brachial artery. Blood was collected before (baseline) and during mental stress (MS) for measurement of nitrite (chemiluminescence) and endothelin-1 (ELISA kit). The AT1R blocker was able to reverse the MS responses observed in the placebo session for retrograde flow (p < 0.01), retrograde SR (p < 0.01) and oscillatory shear index (p = 0.01). Regarding vasoactive substances, no differences were observed in ET-1 (p > 0.05) responses to MS between experimental sessions. However, for nitrite responses, the administration of the AT1R blocker was able to increase circulating levels of NO (p = 0.03) Blockade of AT1R appears to prevent the decrease in endothelial function by reducing low shear stress and maintaining the vasoactive substances balance after MS in overweight/obese men.

Aldosterone secretion during the day: Salivary aldosterone awakening response and daytime levels

BACKGROUND

The mineralocorticoid hormone aldosterone is a key regulator of the sodium-potassium balance and blood pressure. In excess, aldosterone relates to hypertension and cardiovascular disease (CVD). Here, we systematically investigated aldosterone secretion during the day in terms of salivary aldosterone awakening response (AldAR) and salivary aldosterone daytime levels (AldDay) under controlled conditions in participants' natural environment including assessment of potential confounding variables.

METHODS

In 40 healthy young men, saliva samples for AldAR were collected immediately after awakening and 15, 30, 45, and 60 min thereafter. AldDay levels were measured in 1 h intervals from 9:00-22:00 h. Analyses were complemented by salivary cortisol assessment. Fluid and food intake was standardized and as potential confounders, we assessed awakening time and sleep duration, age, BMI and MAP, as well as chronic stress.

RESULTS

Awakening was followed by significant increases in salivary aldosterone (p = .004, f= 0.31), returning to baseline levels > 60 min later. Longer sleep duration was associated with lower AldAR (p < .001, f= 0.36). Over the course of the day we observed a continuous decrease of AldDay (p < .001, f= 0.45). Longer sleep duration (p = .097, f= .21), later time of awakening (p < .001, f= .29), and higher chronic stress (p = .041, f= .23) were associated with AldDay characteristics. Circadian aldosterone secretion was positively associated with most cortisol measures.

CONCLUSIONS

We observed an awakening response in salivary aldosterone and could confirm a decrease in aldosterone levels during the day, comparable to cortisol. Significant confounders were sleep-related variables and chronic stress. Clinical implications of circadian aldosterone secretion with respect to CVD risk remain to be elucidated.